Fractures of the thoracolumbar region of the spine are serious disabling injuries, resulting in personal suffering and significant loss to society. Short segment fixations (pedicle screw and anterior devices) are increasing rapidly in use, and have the advantage of immobilizing only the minimum necessary number of spinal segments. There are two aspects of these devices that are clinically important: reduction of spinal canal and intervertebral foramen encroachments and stabilization of the fractured spine. The strength of the spinal devices has been studied. However, their capability to stabilize the spine in multiple physiological directions is often left out from experimental studies. Device failures are not uncommon, but the failure may be less related to the device strength than to its ability to stabilize. Stability of the fracture site is necessary to enhance the chances of early fusion, thus unloading the device and prevention of its failure. There are no biomechanical studies, using a realistic thoracolumbar burst fracture model, that have studied the adjustments of the short segment fixation devices to both optimize the spinal canal and intervertebral foramen encroachments, and the multidirectional stability provided by the devices. Fresh thoracolumbar human spine specimens will be subjected to high speed trauma that will result in clinically relevant burst fractures. Utilizing a unique incremental trauma approach, the applicants will produce burst fractures of varying severities. Using an innovative model to study a generic short segment device, general criteria for reducing the spinal canal and intervertebral foramen encroachment will be established. Additional experiments will be conducted with specific anterior and posterior devices to determine clinically relevant guidelines for their optimal use. On a comparative basis, the applicants will study the restoration of multidirectional stability of burst fractures of varying severities by the application of anterior and posterior devices, alone and when combined. Pedicle fixation devices are increasing in popularity, but there is concern from government agencies and controversy among orthopaedic and neurosurgical spine surgeons regarding their efficacy and safety. Biomechanical studies can provide objective data to help resolve these controversies. The proposed applicants suggest that the studies optimize one of the most frequently used surgical procedures for spinal fixation. They feel that the findings will result in objective guidelines for the surgeon and treatment benefits for the patient. Clinical relevance is the primary aim of the study, and it may help in the health care cost containment at the level of treatment.